It was found that Fas/FasL pathway is mainly involved in mediating the apoptosis induced by cytotoxicity during T-cell development, while PDAC tumor cells antagonize the apoptosis of CD8+T cells in pancreatic cancer through Fas/FasL pathway, which leads to the down-regulation of Fas expression and the obstruction of the killing pathway of effector T cells to tumor cells, resulting in drug resistance (155). The gene discussed is CD8A; the disease is familial pancreatic carcinoma.